Amplitude scaling for AVO analysis of CSP gathers

Shuang Sun and John C. Bancroft

ABSTRACT

The observation of amplitude variation with offset (AVO) or amplitude variation
with angle of incidence (AVA) can give the information of lithology change in the
subsurface, which has led to several successful cases of finding oil. AVO or AVA
analysis, which is done in common-midpoint (CMP) gathers of un-migrated data
often lacks accuracy due to the effects of CMP smearing. It is worth analyzing AVO
in common-reflection-point (CRP) gathers after prestack migration.

This paper first introduces the concepts of equivalent offset and common-scatter-
point (CSP) gathers, and derives the relationship between equivalent offset and
incident angle for one CRP. It then analyzes four reasonable amplitude scaling factors
during CSP gathering, applies them to synthetic data and compares the results. The
paper also investigates the possibility of analyzing AVO behavior in CSP gathers for
horizontal reflectors. Finally, it applies the most suitable factor to real data.